8 baby leeks
1 lemon, juice only
400g/14oz watercress, leaves picked, half of the stalks retained and finely chopped
200ml/7fl oz chicken stock
200ml/7fl oz chicken stock, boiled, then kept hot over a low heat
salt and freshly ground black pepper
12 cobnuts, shells removed, roughly chopped
olive oil, for drizzling
salt
2 tbsp vegetable oil
110g/4oz unsalted butter
50g/2oz unsalted butter
2 pieces butter wrapping paper
4 x 125g/4½oz halibut fillets
12 quails' eggs